The present invention relates generally to reliability assessment of a power system and more particularly to a system and method for reliability assessment of a power system having integrated components.
Typical power systems include individual components such as breakers, disconnectors, grounding switches, tie breakers, potential transformers (PT), current transformers (CT), and the like. An individual component typically handles one function for the power system. The term power system is defined herein as a system having components for transmission and/or distribution of electrical power and includes any portion of the entire power system. For example, the power system may be an entire power transmission and distribution system, a substation, a plurality of substations, a section of a transmission line, a section of a distribution line, and the like.
When a fault or maintenance occurs on an individual component, the individual component should be electrically isolated from live power to be safely repaired or maintained. This is typically accomplished by opening breakers between the faulted component and any power source. After that, disconnectors around the faulted component are opened. The opened breakers and disconnectors protect personnel from being exposed to live power on the component being repaired or maintained.
Faulted components affect the reliability of power systems in many ways. For example, the faulted component is first isolated from the power system, then repaired, and then the power system is restored back to normal operation. Each of these operations takes a certain amount of time to accomplish. In the same manner, maintenance of components affects the reliability of power systems. That is, the maintained component is first isolated from the power system, then maintained, and then the power system is restored back to normal operation.
To quantify the frequency and the amount of time that a component is expected to be unavailable in the power system (i.e., due to a fault or maintenance), a reliability assessment is performed to calculate reliability for each component in the power system. For example, a reliability assessment may calculate, for each component a total outage frequency (e.g., the expected number of times that a component will be de-energized per year). The total outage frequency includes an outage frequency due to a component fault (e.g., the expected number of times that a component will be de-energized due to a component fault), a self maintenance outage frequency (e.g., the expected number of times that a component will be de-energized due to a maintenance of that component), and an other maintenance frequency (e.g., the expected number of times that a component will be de-energized due to maintenance of another component), and the like.
Conventional reliability systems are described in the following publications, all of which are hereby incorporated by reference in their entirety: R. E. Brown, xe2x80x9cProbabilistic Reliability and Risk Assessment of Electric Power Distribution Systems,xe2x80x9d DistrubuTECH Conference, San Diego, Calif., February 2001, and R. E. Brown, T. M. Taylor, xe2x80x9cModeling the Impact of Substations on Distribution Reliability,xe2x80x9d IEEE Transactions on Power Systems, Vol. 14, No. 1, February 1999, pp. 349-354.
One type of reliability assessment is referred to as an analytical simulation. The analytical simulation models each system contingency, computes the impact of each contingency, and weighs the impact based upon the expected frequency of the system contingency. This model can accurately model complex system behavior by dynamically enumerating each possible system state. This model uses historical data about reliability and repair and maintenance times and produces expected outage times and duration.
Another type of reliability assessment is referred to as a Monte Carlo simulation. This simulation is similar to the analytical simulation; however, this simulation models random contingencies rather than expected contingencies. This allows components to be modeled with probability distributions rather than expected frequencies. Monte Carlo simulation can model complex system behavior and produces a distribution of possible results rather than expected outage times and duration.
Currently, many companies in the power industry are marketing new types of integrated components for power systems. One such integrated component is a Gas-Insulated Module (GIM). The GIM combines several individual components together in one gas chamber. For example a GIM may include a breaker, a disconnector, a grounding switch, and a PT integrated in one module (i.e., an integrated component).
To repair or maintain a GIM, not only should the faulted individual component be isolated, but because of the proximity of the individual components, the entire GIM should be isolated to be safely repaired or maintained.
Another such integrated component is an Air-Insulated Module (AIM). The AIM combines several individual components together. For example a AIM may include a breaker, a disconnector, a grounding switch, and a PT integrated in one module (i.e., an integrated component). The breaker of the AIM is typically a removable component. That is, the breaker can be removed from the AIM and then repaired.
To repair or maintain an AIM, not only should the faulted individual component be isolated, but because of the proximity of the individual components, the entire AIM should be isolated to be safely repaired or maintained. However, if the faulted component is the removable component, the AIM may be isolated, the faulted component removed for repairing, and the power to the non-removable components of AIM restored.
Conventional reliability assessment systems are designed for a power system having only individual components, rather than having integrated components. Therefore, conventional reliability assessments yield incorrect results when applied to a power system including integrated components. When a power system includes one or more integrated components as well as individual components, conventional reliability assessments may yield even more inaccurate results. With the recent deregulation of power utilities, reliability assessment of power systems is critical for success in the market.
Therefore, a need exists for a system and method for reliability assessment for a power system having an integrated component. Moreover, in light of ever-evolving integrated component design, a need exists for a system and method with the capability to model a newly created integrated component.
The present invention is directed to a system and method for reliability assessment of a power system having an integrated component.
According to an aspect of the present invention, a system and method is provided for performing a reliability assessment of a power system having an integrated component. The integrated component can be modeled with information about the individual components of the integrated component. Individual component failure rates associated with individual components of the integrated component are retrieved from a data store and a failure rate for the integrated component is determined based on the individual component failure rates. The individual components may include a bushing including a current transformer and a voltage transformer and determining a circuit breaker, a disconnector, a grounding switch, a bushing, a current transformer, a potential transformer, and the like.
According to another aspect of the present invention, a failure time of an individual component associated with an integrated component is used to model the failure time of the integrated component. The failure time may be a mean time to repair.
According to yet another aspect of the present invention, a maintenance frequency of an individual component associated with an integrated component is used to model the maintenance frequency of the integrated component.
According to a further aspect of the present invention, a maintenance time of an individual component associated with an integrated component is used to model the maintenance time of the integrated component. The maintenance time may be a mean time to maintain.
According to another aspect of the present invention, information representative of interconnectivity of individual components of the power system is retrieved and information representative of which individual components are associated with an integrated component is retrieved. The information allows determination of which individual components are associated with an integrated component and fault and maintenance simulations can therefore, be performed accordingly.
According to yet another aspect of the present invention, a reliability assessment is determined based on the interconnectivity information, the information representative of which individual components are associated with an integrated component, the modeled maintenance frequency and time of integrated components of the power system, and the modeled failure rate and time of the integrated components of the power system.
According to a further aspect of the present invention, an integrated component may be a pre-defined integrated component or a user-defined integrated component.
These and other features of the present invention will be more fully set forth hereinafter.